Bosch 250SX NG, 250SX LP User Manual

MODEL 250SX NG and 250SX LP

Temperature Modulated with Electronic Ignition

Suitable for heating potable water only

Not approved for space heating purposes

(Intended for variable flow applications with multiple tapping points)

250 SX NG
250 SX LP

Warning: If the information in this manual is not

followed exactly, a fire or explosion may result
causing property damage, personal injury or death.
Do not store or use gasoline or other flammable
vapor and liquids in the vicinity of this or any other
appliance.

Improper installation, adjustment, alteration,
service or maintenance can cause injury or
property damage. Refer to this manual. For
assistance or additional information consult a
qualified installer, service agency or the gas
supplier.
In the Commonwealth of Massachusetts this
product must be installed by a licensed plumber or
gas fitter.

Upon completion of the installation, these
instructions should be handed to the user of the
appliance for future reference.

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What to do if you smell gas

• Close gas valve. Open windows.

• Do not try to light any appliance.

• Do not touch any electrical switch; do not use any
phone in your building.

• If you cannot reach your gas supplier, call the fire
department.

• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions

• Installation and service must be performed by a
qualified installer, service agency or the gas supplier.

Index

Index

1Warning 2

2 Appliance details 4

2.1 Features 4

2.2 250 SX Specifications (Technical data) 4

2.3 Dimensions and Minimum installation clearances 6

2.4 General rules to follow for safe operation 7

2.5 Proper location for installing your heater 7

2.6 Clearances 8

2.7 Mounting installation 8

2.8 Combustion air requirements 8

2.9 Venting 9

2.9.1 Venting options 11

2.10 Gas piping & connections 15

2.11 Gas line sizing 17

2.12 Measuring gas pressure 17

2.13 Water connections 18

2.14 Electrical connections 19

2.15 Operating instructions 19

2.16 For your safety read before operating your water heater 19

2.17 Lighting and operating instructions 19

3 Operation instructions 21

3.1 Power 21

3.2 Temperature selection 21

3.3 Use of remote control accessory 23

3.4 Operation 23

3.5 Reset button 23

3.6 Program button 23

3.7 Locked condition 23

1Warning

Warning: If the information in this

manual is not followed exactly. A fire or
explosion may result causing property
damage, personal injury or death.

Warning: Improper installation,
adjustment, alteration, service or
maintenance can cause injury or
property damage. Refer to this manual.
For assistance or additional information
consult a qualified installer, service
agency or the gas supplier.
Upon completion of the installation,
these instructions should be handed to
the user of the appliance for future
reference.

Featuring

Electronic Ignition and Power Venting

For your safety

Do not store or use gasoline or other flammable,
combustible or corrosive vapors and liquids in the
vicinity of this or any other appliance.

4 Maintenance and service 24

5 Troubleshooting 24

6 Electrical diagram 27

7 250 SX Functional scheme 28

8 Interior components diagram and parts list 29

8.1 Interior components 29

8.2 Components diagram 30

8.3 Parts list 31

9 Special adjustment for measuring and adjusting CO2

levels 32

9.1 Adjusting the unit 32

9.1.1 CO2 measuring port 32

9.1.2 Selecting adjustment mode 32

10 Protecting the environment 34

11 Twelve Year Limited Warranty 35

Warning: Carefully plan where you

install the heater. Correct combustion
air supply and flue pipe installation are
very important. If a gas appliance is not
installed correctly, fatal accidents can
result from lack of air, carbon monoxide
poisoning or fire.

Warning: Exhaust gas must be vented
to outside using proper vent material
suitable for category III vent systems
and temperatures up to 480°F. Vent
and combustion air connector piping
must be sealed gas-tight to prevent
possibility of flue gas spillage, carbon
monoxide emissions and risk of fire,
resulting in severe personal injury or
death.

Warning: Place the heater in a location
where water leaks will do NO DAMAGE
to adjacent areas or lower floors.

2

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Warning: Field wiring connections and
electrical grounding must comply with
local codes, or in the absence of local
codes, with the latest edition of the
National Electric Code, ANSI/NFPA 70,
or in Canada, all electrical wiring must
comply with the local codes and the
Canadian Electrical Code, CSA C22.1
Part 1.

Warning: Shock hazard line voltage is
present. Before servicing the water
heater, turn off the electrical power to
the water heater at the main disconnect
or circuit breaker. Failure to do so could
result in severe personal injury or death.

What to do if you smell gas

• Close gas valve. Open windows.

• Do not try to light any appliance.

• Do not touch any electrical switch; do not use any
phone in your building.

• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.

• If you cannot reach your gas supplier, call the fire
department.

• Installation and service must be performed by a
qualified installer, service agency or the gas supplier.

Warning

Fig. 1

Warning: The heater must be
disconnected from the gas supply
piping system during any pressure
testing of that system at test pressures
equal to or more than 0.5 psig.

FCC:
This device complies with Part 15 of the FCC rules.
Operation is subject to the following two conditions: (1)
This device may not cause harmful interference, and (2)
this device must accept any interference received,
including interference that may cause undesired
operation.

Caution: Any changes or
modifications not expressly approved
by the party responsible for compliance
could void the user’s authority to
operate the equipment.

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Fig. 2

3

Appliance details

2 Appliance details

2.1 Features

Parts

• Touch Pad interface control

• High power pre-mix compact burner with low Nox
emissions

• Modulating Gas Valve with constant gas:air ratio
control

• Modulating water valve for improved comfort and
temperature control.

Safety

• Flame sensor (ionization) rod

• Overheat sensor

• Temperature limiter

• Fan speed monitoring.

High Quality Materials for Long Working Life

• Copper heat exchanger

• Ceramic Burner output

• Automatic overheating protection shut-off sensor

• Compact space saver: mounts on a wall with a
supplied bracket.

• Easily removable one-piece cover.

Features

• LCD Display

• On/Off and Temperature control switches

• Reset button

• Program Key (Selectable temperature default)

• Failure codes for easy diagnostic and repair.

Accessories

• Optional wireless remote control accessory to
operate with the appliance

Maximum input

175,000 Btu/h (51.2 kW)

Efficiency in %

Recovery efficiency 86.5%

Min. Output

31,131 Btu/h (9.1 kW)

Temperature Control

Selection range: 100°F (38°C) - 140°F (60°C)
Default temperature: 122°F (50°C)
Stability: +/- 2°F (+/- 1°C)

Gas Requirement

Gas connection (inches) - ¾”
Inlet gas pressure under operation (with a high hot

water flow rate)*

• Propane: 11” - 14” water column

• Natural Gas: 5” - 14” water column

• Gas pressure measuring point inside the appliance
at the gas valve inlet.

* Testing with a manometer, operate other gas
equipment on the same gas supply. Gas pressures
lower than 5" W.C. for Natural Gas or 11" W.C. for
LPG will result in insufficient degree rise to the hot
water being used. See Measuring Gas Pressure,
chapter 2.12.

• Vent termination kit.

BOSCH is constantly improving its
products, therefore specifications are

i

subject to change without prior notice.

2.2 250 SX Specifications (Technical
data)

Approved in US/Canada

Capacity

Maximum flow rate: 6.35 GPM (24 l/min) at a 45°F
(25°C) rise.

Maximum output

142,968 Btu/h (41.8 kW)

4

Fig. 3 Gas pressure measuring point

Venting

See chapter 2.9 for Venting on page 9.

Water

• Hot water connection (inches) - ¾”

• Cold water connection (inches) - ¾”

• Water valve material: Polymer (PPS) (Polypropylene
Sulfid)

• Minimum water flow: 0.8 gallon/minute (3 l/m)

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Appliance details

• Minimum recommended water pressure: 30 PSI
(2.07 bar)

• Connections:
– Bottom of heater

Combustion

•NOx ≤ 55 ppm

•CO ≤ 250 ppm

•CO

level set from factory, see chapter 9.1.

2

Dimensions

• Depth (in): 8 ½” (220 mm)

• Width (in): 15 ¾” (400 mm)

• Height (in): 23 ½” (600 mm)

• Weight: 47 pounds (21 kg).

Gas types

Natural Gas.
LP Gas.
Converting the gas type can only be done by a certified
gas technician with a calibrated CO

analyzer. Call

2

CEC for conversion instructions.

Voltage

120 V AC (50/60 Hz)

Amperage

IDLE - 40 mA
Operation - ≤ 2,5 A

Noise

≤ 50 db (A)

UNPACKING THE 250 SX HEATER

This heater is packed securely.
The box includes:

• Pressure relief valve

• Bracket for wall hanging the heater

• Exhaust vent adaptor (with 4 screws and gasket
provided)

• Combustion air inlet adaptor (with 3 screws and gas­ket provided)

• Plastic decal shields for covering front cover screws
and control panel, installer should affix these decals
to the front of the unit after installation is complete.
See Fig. 4

• Installation manual

• Product registration card.

Do not lose this manual. Please complete and return
the enclosed product registration card.

Before installing the unit, be certain you have the
correct heater for your type of Gas - Propane or
Natural Gas. Identification labels are found on the

shipping box, and on the rating plate which is located on
the right side panel of the cover.

To remove front cover

• Loosen the two Philips head screws located on front
panel (beneath plastic decal shields if they are
already attached, see Fig. 4)

• Lift front cover panel upward and remove.

Safety devices

• Flame failure device (ionization flame rod sensor)

• Pressure relief valve (supplied with heater)

• Over heat prevention (temperature limiter).

Water resistant

IP X4 (protection against water drops)

Plastic decals

Fig. 4 Remove front cover

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5

Appliance details

2.3 Dimensions and Minimum installation clearances

Fig. 5 Dimensions

1 Cover
2 On/Off switch
3 Reset button
4 LCD display
5 Program button
6 Temperature buttons

Fig. 6 Minimum clearances

Model 250 SX

TOP (A) 12”

FRONT (B) 4”
BACK 0”

SIDES 4”

FLOOR (C) 12”

VENT DIAMETER 3”

Table 1 Minimum clearances

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Appliance details

2.4 General rules to follow for safe
operation

B 1. You should follow these instructions when you

install your heater. In the United States: The
installation must conform with local codes or, in the
absence of local codes, the National Fuel Gas Code
ANSI Z223.1/NFPA 54.
In Canada: The Installation should conform with
CGA B149.(1,2) INSTALLATION CODES and /or
local installation codes.

B 2. Carefully plan where you install the heater. Correct

combustion air supply and vent pipe installation are
very important. If not installed correctly, fatal
accidents can be caused by lack of air, carbon
monoxide poisoning or fire.

B 3. When the unit is installed indoors and ROOM

SEALED (twin pipe) it is permitted to be located in
bathrooms, bedrooms and occupied rooms that are
normally kept closed. See chapter 2.9. If the unit will
be installed indoors and use indoor combustion air,
the place where you install the heater must have
enough ventilation. The National Fire Codes do

not allow UNSEALED gas fired water heater
installations in bathrooms, bedrooms or any
occupied rooms normally kept closed. See

chapter 2.5 and 2.8.

B 4. You must vent your heater. See section on

VENTING.

B 5. The appliance must be isolated from the gas

supply piping system by closing its individual manual
gas shutoff valve (not supplied with heater) during
any pressure testing at pressures in excess of ½ Psig
(3.5 kPa).
The appliance and its gas connection must be leak
tested before placing the appliance in operation.

B 6. Keep water heater area clear and free from

combustibles and flammable liquids. Do not locate
the heater over any material which might burn.

B 7. Correct gas pressure is critical for the optimum

operation of this heater. Gas piping must be sized to
provide the required pressure at the maximum output
of the heater, while all the other gas appliances are in
operation. Check with your local gas supplier, and
see the section on connecting the gas supply.

B 8. Should overheating occur or the gas supply fail to

shut off, turn off the gas supply at the manual gas
shut off valve, on the gas line. Note: manual gas
shutoff valve is not supplied with the heater.

B 9. Do not use this appliance if any part has been

underwater. Immediately call a qualified service
technician to inspect the appliance and to replace
any part of the control system and any gas control
which has been underwater

2.5 Proper location for installing your
heater

Carefully select the location of the water heater. For
your safety and for proper heater operation, you must
provide combustion air to the heater and a proper
exhaust vent system.
Follow the guidelines below:

B 1. Locate the heater where venting, gas and

plumbing connections are feasible and convenient.

B 2. It is strongly recommended that the heater be

installed as a ROOM SEALED heater (twin pipe). If
the heater will be installed as an UNSEALED heater
(single pipe) than National building codes require
that you do not install this appliance in bathrooms,
bedrooms or any occupied rooms normally kept
closed. Heaters that are UNSEALED require a
considerable amount of combustion air, see
chapter 2.8. If installing the heater UNSEALED
within a laundry room, be certain that the dryer is
properly vented. Failure to properly vent a dryer could
result in a gradual accumulation of lint build up inside
the combustion chamber of the heater.

B 3. The hot water lines should be kept short to save

energy. Centrally locating the water heater is best. It
is always best to have hot water lines insulated.

Warning: The water in this water
heater is cold and always remains cold
except for the times that hot water is
being used DO NOT INSTALL IN AN
AREA WHERE IT COULD FREEZE.
Drain the heater entirely if freezing
temperatures are anticipated in area
where heater is installed by
disconnecting both the inlet and outlet
connections at the bottom of heater.
To prevent any freeze damage,
introduce short bursts of compressed
air (20-40psi) through these
connections to remove the residual
water in the horizontal pipes and water
valve.

Warning: Flammable materials,
gasoline, pressurized containers, or any
other items or articles that are potential
fire hazards must NOT be placed on or
adjacent to the heater. The appliance
area must be kept free of all
combustible materials, gasoline and
other flammable vapors and liquids.

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7

Appliance details

2.6 Clearances

The 250 SX is design certified for installation on a
combustible wall (see 2.7 Mounting installation)
provided the floor covering below the heater is
noncombustible. For installations in an alcove or closet,
maintain the minimum clearances to combustible and
non-combustible materials listed below. See also Fig. 6.

A. Top 12 inches (306 mm)
B. Front 4 inches (102 mm)
C. Back 0 inches
D. Sides 4 inches (102 mm)
E. Bottom 12 inches (306 mm)

Clearances from any exhaust vent pipe are dependent
upon the clearance requirements of the stainless steel
vent pipe manufacturer. Single wall stainless steel
(AL29-4C) vent pipe (vent type rated for Category III
appliances) must be used when exhaust venting this
appliance. See 2.9 Venting.

2.7 Mounting installation

Warning: before starting installation:

B check that there are no loose parts

inside the appliance

B ensure that gas pipe, gas valve, mixer,

fan and burner have no damage and are
properly fitted.

Front cover should be removed (see
instructions on page 4) in order to inspect

i

components visually.

The 250 SX is design certified for mounting on a wall.
Secure the wall mounting bracket provided with the
heater to a wall surface. See Fig. 7.
Do not install this appliance on a carpeted wall or over
floor covering which is combustible, such as carpet.
The heater must be mounted on a wall using
appropriate anchoring materials.
If the mounting bracket is unable to line up on two wall
studs it is recommended that support board(s), either
1x4's or ½" (minimum) plywood first be attached across
a pair of studs and then the heater should be attached
to the support boards. The heater should be kept level
on the wall surface. See Fig. 7.
Expansion and contraction of piping due to changing
water temperature in the pipes imparts movement to the
heater which, if mounted directly to a brittle, friable
board, such as plasterboard, can cause failure of
mounting.

Before installing the unit, be certain you have the
correct heater for your type of Gas - Propane or
Natural Gas. Identification labels are found on the

shipping box, and on the rating plate which is located on
the right side panel of the cover.

Fig. 7 Mounting the heater

2.8 Combustion air requirements

The 250 SX is a sealed water heater and it is
recommended that outdoor combustion air be piped to
the unit. When combustion air is piped to the unit
(TWIN PIPE SYSTEM) the combustion air pipe system
may be constructed of either 3" PVC, aluminum or
galvanized pipe. See Fig. 11, 12 and 13. Select a point
for building penetration being sure that the necessary
clearance on the outside of the building, between the
combustion air pipe and the exhaust vent terminator of
the appliance, can be maintained, see Fig. 16. NOTE:
Observe all local building codes when penetrating a
building wall.

NOTE: The combustion air inlet location on the
side of a building must never be less than 3 feet
away from the units exhaust vent terminator, see
Fig. 16 Table 3.

The heater has the ability to operate without
combustion air being piped to it from the outside,
provided there is an adequate amount of combustion air
available in the room area. Observe the following
instructions concerning combustion air when following
the SINGLE PIPE (exhaust venting only) SYSTEM only
and follow Fig. 14 and 15 for proper setup.

• Appliances located in unconfined spaces:
– a) An unconfined space is one whose volume is

greater than 50 cubic feet (1.42 cubic meter) per
1000 Btu per hour (292.81 Watts) of the
combined rating of all appliances installed in the
space. That would be 8750 cubic feet (247.8
cubic meter) for the 250 SX alone.

8

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Appliance details

– b) In unconfined spaces in buildings of

conventional frame, masonry, or metal
construction, infiltration air is normally adequate to
provide air for combustion.

• Appliances located in confined spaces:
The confined space must be provided with two
permanent openings, one commencing within 12
inches (304.8mm) of the top and one commencing
within 12 inches (304.8mm) of the bottom of the
enclosure. Each opening must have a minimum free
area of one square inch per:

– 1000 Btu/hr (292.81 Watts) if all air is taken from

inside the building

– 2000 Btu/hr (585.62 Watts) if all air is taken from

the outside by horizontal ducts

– 4000 Btu/hr (1171.24 Watts)if all air is taken from

the outside by direct openings or vertical ducts

Or the confined space must be provided with one
permanent opening or duct that is within 12 inches
(304.8mm) of the ceiling of the enclosure. This opening
must have a minimum free area of one square inch per:

– 3000 Btu/hr (878.43 Watts) if all air is taken from

the outside by a direct opening or vertical duct.

Louvers, grills and screens have a blocking effect. If the
effective free area is not known, increase the sizes of
your openings by 75% if your louvers are wood and by
30% if your louvers are metal. Refer to the National Fuel
Gas Code for complete information. In buildings of tight
construction all air should be taken from outside.

Establish vent clearances that comply with the vent
manufacturer's specifications. In all cases follow local
codes. See table 2.

2.9 Venting

Warning: Do not reduce the vent

(exhaust and combustion) pipe sizes
and do not common vent with any other
vented appliance or stove.

NOTE: This appliance's exhaust must be vented
to the outside with a sealed 3" stainless steel
vent pipe (AL29-4C). The appliance's flue gasses
are under positive pressure and must travel
through a stainless steel 3" pipe that is sealed
gas tight. Stainless steel vent pipe is equipped
with sealing gaskets for ease of installation,
proper safety and durability. The heater shall not
be vented in combination with any other
appliance; the appliance must only be vented
with a dedicated sealed vent system.

Caution: The vent system must be

installed by a qualified agency in
accordance with these instructions. If
improperly installed a hazardous
condition such as explosion or Carbon
Monoxide poisoning could result. CEC
will not be responsible for improperly
installed appliances.

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9

Appliance details

The maximum flue gas exhaust temperature on the 250 SX is 437°F (225°C)

Venting
Options

Room
s ea l ed
(twin pipe)

Open
combustion
(single
pipe)

Exhaust vent is always fan assisted. Installation of exhaust vent and combustion air piping may be run vertically or horizontally
and in separate directions if required.

* A maximum of three 90 degree elbows are permitted in the total vent length. The total vent length must be reduced by 1 ¼
feet for every 45° elbow used in the vent system.
** Stainless steel (AL29-4C) vent pipe is manufacturerd by Z-Flex, Protech and Heat Fab. NOTE: clearance distances are
variable depending if the vent pipe is installed in an enclosed or unenclosed space, the exhaust flue gas temperature and the
orientation of the vent pipe.

Exhaust
vent
diameter
and
material

3 inch
stainless
steel
(AL29-4C)
sealed vent
pipe

3 inch
stainless
steel
(AL29-4C)
sealed vent
pipe

* Exhaust
vent
maximum
length

26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
90° elbow

26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
90° elbow

* Exhaust
vent
minimum
length

3 feet 3 inch PVC,

3 feet See

Combustion
air pipe
diameter
and material

aluminum or
galvanized
pipe

chapter 2.8

Combustion
air pipe
maximum
length

26 feet (8
m) with one
elbow. Less
2½ feet for
each
additional
90° elbow

See
chapter 2.8

Vent pipe
clearances
within an
unenclosed
space

** See vent
manufacturer's
specifications

** See vent
manufacturer's
specifications

Vent pipe
clearances
within an
enclosed
space

** See vent
manufacturer's
specifications

** See vent
manufacturer's
specifications

Table 2

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Appliance details

The appliance should be located as close to the point
of termination as possible. The maximum vent length is
26 feet (8 m) with one 90 degree elbow. Subtract 2½
feet from the total vent length for each additional 90°
elbow used (a maximum of three 90° elbows are
permitted in the total vent length), or subtract 1 ¼ feet
for every 45° elbow used. Horizontal sections of vent
must pitch ¼" for every foot of horizontal length and be
supported at 4 foot intervals with overhead hangers.
Note: Listed thimbles or collars are necessary to pass
through wall and ceiling partitions. If the vent system
passes through combustible areas where the vent
clearance requirements cannot be maintained, it is
permissible to chase straight sections of sealed 3 inch
single wall vent through 4 inch (or greater) Type-B vent.
The distance to combustibles using this chase
technique is 1 inch. Note: Type-B vent should never

be used as the actual exhaust vent system for the
appliance, as it is not gas tight.

Minimum exhaust vent size and length

The use of a 90 degree elbow
is equivalent to 2 ½ ft in vent
length.
The use of 45 degree elbow is
equivalent to 1 ¼ ft in vent
length.

page 24. See error code to confirm error, correct the
problem and then reset the heater before operating.

Attaching the exhaust and air inlet connection
adaptors to the top of the heater

Fig. 10

Fig. 8

Maximum exhaust vent and combustion air inlet
lengths

Fig. 9

Note: reduce 2½ ft for each 90° elbow used after the
first one, reduce 1 ¼ ft for each 45° elbow.

Vent Safety System

The 250 SX will shut down if inadequate exhaust
venting is detected or a lack of combustion air is
provided to the unit; see troubleshooting section on

Fig. 11

B Attach the flue gas exhaust accessory (8 705 504

114) to the top of the unit (position 1) using the 4
screws and gasket provided, and fully insert 3"
stainless steel vent pipe into the accessory and
tighten the clamp (position 2).

B Attach the combustion air inlet accessory (8 705

504 115) to the top of the unit (position 3) using the
3 screws and gasket provided, and fully insert 3"
combustion air pipe into the accessory and tighten
the clamp (position 4). NOTE: The appliance has the
possibility to mount the combustion air inlet
accessory on the top right or on the top left side of
the heater. The combustion air inlet that is not used
must be kept sealed.

2.9.1 Venting options

Installing this water heater as a room sealed (TWIN
PIPE SYSTEM) is the recommended method. Contact
CEC or dealer for available vent termination kits and
vent materials for this water heater.

Exhaust venting shall be done with 3”
stainless steel (AL29-4C) vent pipe.

i

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11

Appliance details

Room sealed installation (TWIN PIPE SYSTEM)

Fig. 12

Combustion air pipe: ≤ 26 ft (8 m)
Exhaust vent pipe: ≤ 26 ft (8 m)
If the total horizontal exhaust vent length in a side wall
installation is greater than or equal to 5 feet (1.5m), a
condensate drain tube must be attached to the exhaust
collar. See page 14.

Open combustion installation (SINGLE PIPE
SYSTEM)

Fig. 14

Exhaust vent pipe: ≤ 26 ft (8 m)
If the total horizontal exhaust vent length in a side wall
installation is greater than or equal to 5 feet (1.5m), a
condensate drain tube must be attached to the exhaust
collar. See page 14.

Fig. 13

Combustion air pipe: ≤ 26 ft (8 m)
Exhaust vent pipe: A+B+C ≤ 23½ ft (7.2 m)
A condensate drain tube must be attached to the
exhaust collar of the heater for any vertically exhausted
vents, see page 14.

Note: reduce 2½ ft for each 90° elbow used after the
first one, reduce 1 ¼ ft for each 45° elbow.
A maximum of three 90-degree elbows are permitted.

The exhaust vent pipe and combustion air
pipe can be run vertically or horizontally.

i

Maximum length for each individual pipe is
26 feet (8 m) with one elbow, for each
additional 90° elbow after the first elbow
you must reduce 2½ feet from the total
vent length, or 1 ¼ feet for each 45°
elbow.

Fig. 15

Exhaust vent pipe: A+B+C ≤ 23½ ft (7.2 m)
A condensate drain tube must be attached to the
exhaust collar of the heater for any vertically exhausted
vents, see page 14.

The exhaust vent system must vent directly to the
outside of the building and an adequate amount of
indoor combustion air must be provided for this
installation. See chapter 2.8.
Connecting a one piece 90 degree elbow pipe to the
combustion air inlet adaptor is necessary, this will
prevent debris or objects from ever falling into the inlet
opening.
Note: reduce 2½ ft for each elbow used after the first
one, reduce 1 ¼ ft for each 45° elbow.
A maximum of three 90-degree elbows are permitted.

12

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Recommended exhaust vent terminator position

Fig. 16

Appliance details

Ref. Description Minimum distance

A

B

C From any internal corner 12 in

D*

E

F From a terminator facing a terminator 48 in

G Vertically between two exhaust vent terminators on the same wall 60 in

H Horizontally between two exhaust vent terminators on the same wall 12 in

I**

J From any external corner 12 in

K

Directly below an opening; operable windows, doors and any non­mechanical fresh air openings

Below a gutter, sanitary pipework or eaves 24 in
Below a gutter, sanitary pipework or eaves, protected by metal

shielding

Above ground 12 in

Above a paved sidewalk 7 ft

From an opposing wall or structure facing the termination 24 in

From any other building opening, gas utility meter, service regulator
or the like

Horizontally from combustion air inlet of 250 SX

Vertically above or below combustion air inlet of 250 SX

From the combustion air inlet of any other equipment 6 ft

Horizontally from an opening; operable windows, doors and any
non-mechanical fresh air openings

36 in

12 in

36 in

36 in

12 in

L

Vertically from a wall, roof slope, or obstruction (venting through a
flat or pitched roof)

see ABOVE THE ROOF

requirements on following page

Table 3

* Subject to local codes and anticipated snow level
** Other equipment that operates with a mechanical air inlet may require greater distances, reference manufacturer's instructions

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13

Appliance details

Supporting the exhaust vent system and the use
of an external condensate trap

External condensate traps

B A condensate trap must be used in any sidewall

exhaust vent installations when the total vent length
is ≥ 5 ft (1.5 m) OR the vent pipe passes through an
unheated space (below 60F). See diagram below for
connecting a condensate tube.

B A condensate trap must be used for any vertical

exhaust installations. See diagram below for
connecting a condensate tube.

B When installing the condensate tubing at the exhaust

collar (see diagram below), be sure to form a trap by
means of a 3" (76.2 mm) loop filled with water. This
tube must be 3/8" ID high temperature silicone
for at least the first 6 inches (152 mm) and attached
with a gear clamp or hose clamp. The condensate
must be disposed of according to local regulations.

The venting materials and accessories
required to properly install the water

i

heater are available from CEC and their
distributors.

If the total horizontal exhaust vent length in a side wall
installation is greater than or equal to 5 feet (1.5m), a
condensate drain tube must be attached to the exhaust
collar.

Fig. 18 Above the roof clearance requirements from

rain cap (combustion air piping not being
shown)

Condensate port on exhaust collar

Remove the screw from the
condensate tapping

Gear clamp

Condensate
tube/trap

Fig. 17 Horizontal side wall venting installation

(combustion air piping not being shown)

14

Fig. 19 Vertical venting installation (combustion air

piping not being shown)

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Appliance details

A condensate drain tube must be attached to the
exhaust collar of the heater for any vertically exhausted
vents, see page 14.

2.10

Before connecting the gas supply, check the rating
plate on the right side of the heater to be sure that the
heater is rated for the same gas to which it will be
connected.
In the United States: The installation must conform with
local codes or, in the absence of local codes, the
National Fuel Gas Code ANSI Z223.1/NFPA 54.
In Canada: The Installation should conform with CGA
B149 INSTALLATION CODES and/or local installation
codes.

GAS LINE SIZING

The gas supply piping should be sized according to the
Applicable Plumbing Code for a maximum draw of
175,000 BTUH. First determine the effective length of
the gas supply line by measuring the actual length of
piping, and then adding 5 ft. (1.52m) for every elbow or
“T” to the actual length. Use the charts in Fig. 22 to
determine the pipe diameter necessary to
accommodate the BTU (Wh) demand of the unit. If
there are more gas drawing appliances on the line, size
according to the maximum amount of BTU (Wh)
demand.

Note: It is important that if any flexible gas line is used,
above or below ground between the gas supply meter/
regulator and the water heater, that it be sized properly;
we recommend the use of non-corrugated flexible gas
line when used. Consult the gas sizing specification
tables provided by the flexible gas line manufacturer.

Gas piping & connections

Fig. 20 Vertical venting installation - Masonry

Chimney (combustion air piping not being
shown)

A condensate drain tube must be attached to the
exhaust collar of the heater for any vertically exhausted
vents, see page 14.

6 720 607 057

Inlet gas particle screen

Gas piping

Fig. 21

B Install a manual gas shut off valve, on the gas supply

line.

B The use of a union when connecting gas pipe to the

gas inlet connection is critical, this will facilitate any
necessary servicing and cleaning of the inlet gas
particle screen.

B Flexible gas line connectors are not recommended

because they are commonly undersized and restrict
gas flow. Oversize the diameter of any flexible gas
line connector if one must be used.

15

Appliance details

FOR NATURAL GAS

Maximum Capacity of pipe in Cubic Feet of Gas per Hour for Gas Pressure of 0.5 Psig or less and a Pressure drop
of 0.3 in Water Column (0.75mbar).(Based on a 0.60 Specific Gravity Gas) Btu numbers given in thousands.

Follow boxed numbers for piping just one 250 SX
(example: ¾” B.I. Natural Gas pipe for 20 ft (6.1m).
will handle 190,000 btu’s (55.7 kWh). For multiple
appliances combine the total btu input load and then
refer to applicable chart below.

Nominal
Iron Length of Black Iron Pipe, Feet
Pipe Internal
Size, Diameter
inches inches 10 20 30 40 50 60 70 80 90 100 125 150 175 200

1/4 0.364 32 22 18 15 14 12 11 11 10 9 8 8 7 6
3/8 0.493 72 49 40 34 30 27 25 23 22 21 18 17 15 14
1/2 0.622 132 92 73 63 56 50 46 43 40 38 34 31 28 26

3/4 0.824 278 190 152 130 115 105 96 90 84 79 72 64 59 55

1 1.049 520 350 285 245 215 195 180 170 160 150 130 120 110 100

1 1/4 1.380 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
1 1/2 1.610 1600 1100 890 760 670 610 560 530 490 460 410 380 350 320

2 2.067 3050 2100 1650 1450 1270 1150 1050 990 930 870 780 710 650 610

2 1/2 2.469 4800 3300 2700 2300 2000 1850 1700 1600 1500 1400 1250 1130 1050 980

3 3.068 8500 5900 4700 4100 3600 3250 3000 2800 2600 2500 2200 2000 1850 1700
4 4.026 17,500 12,000 9,700 8,300 7,400 6,80 6,200 5,800 5,400 5,100 4,500 4,100 3,800 3500

FOR LP GAS

Maximum C apacity of Pipe in Thousands of BTU per
Hour of Undiluted Petroleum Gases (at 11 inches
Water Column Inlet Pressure) (Based on a Pressure
Drop of 0.5 Inch Water Column).

Maximum Capacity of Semi-Rigid (flexible, non
corrugated) Tubing in Thousands of BTU per Hour
of Undiluted Liquefied Petroleum Gases (at 11
inches Water Column Inlet Pressure).

(Based on a Pressure Drop of 0.5 Inch Water
Column)

* Source National Fuel Gas Code NFPA 54, ANSI
Z223.1 - No Additional Allowance is necessary for an
ordinary number of fittings

Nominal

Iron Pipe

Size,

Inches

Outside Length of Tubing, Feet
Diameter,
Inch 10 20 30 40 50 60 70 80 90 100

10 20 30 40 50 60 70 80 90 100 125 150

1/2 275 189 152 129 114 103 96 89 83 78 69 63

3/4 567 693 315 267 237 217 196 185 173 162 146 132
1 107 732 590 504 448 409 378 346 322 307 275 252
1 1/4 220 149 121 103 913 834 771 724 677 630 567 511
1 1/2 330 229 185 155 141 127 118 108 102 976 866 787
2 622 433 346 299 264 239 220 204 192 1811 1606 1496

3/8 39 26 21 19 _ _____

1/2 9262 50 41 37 3531292726

5/819913110790 79 7267625955

3/4 329 216 181 145 131 121 112 104 95 90

7/8 501 346 277 233 198 187 164 155 146 138

Black Iron Pipe
Length of Pipe, Feet

Copper

Fig. 22

16

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Appliance details

2.11 Gas line sizing

B It is strongly recommended that the Natural Gas pipe

be Black Iron pipe the entire distance from the
outside meter to the inlet of the gas connection. ¾”
Black Iron pipe up to 20 feet (6.1m) and 1” Black Iron
pipe up to 70 feet (21.34m) distances. Flex line is
NOT recommended, but if used, then oversize the
diameter of the flex pipe, keep the length to a
minimum and try to keep the flex line as straight as
possible.

B It is strongly recommended that the LP Gas pipe be

semi-rigid copper or Black Iron pipe from the outside
regulator to the inlet of the gas connection. For semi­rigid copper piping: 5/8” up to 10 feet (3.05m) and
¾” up to 30 feet (9.14m) distances. For Black Iron
piping: ½” up to 20 feet (6.1m) and ¾” up to 80 feet
(24.38m) distances. Flex line is NOT recommended,
but if used, then oversize the diameter of the flex
pipe, keep the length to a minimum and try to keep
the flex line as straight as possible.

THESE FIGURES ARE FOR 250 SX
SUPPLY ONLY, ALL OTHER

i

APPLIANCES IN THE BUILDING MUST
BE INCLUDED IN THE PIPE SIZING.

load. Using a manometer, then measure the inlet gas
pressure at the inlet gas pressure test port. See Fig. 23.
Gas pressures lower than 5" W.C. for Natural Gas or
11" W.C. for LPG will result in insufficient degree rise
to the hot water being used. See Gas Connections,
chapter 2.10.

Fig. 23 Gas pressure measuring (left tapping)

HIGH ALTITUDE OPERATION

Due to the lower density of air at high altitudes, output
must be reduced in installations above 4,000 ft (1,219
m).

Altitude Natural Gas: Liquid

Propane:

National Fuel Gas Code requires that a sediment trap
(drip leg) be installed on gas appliances not so
equipped. Also, a manual gas shut off valve must be
installed on the gas supply line within close proximity of
the water heater and be visible from the water heater.

Warning: The heater must be
disconnected from the gas supply
piping system during any pressure
testing of that system at test pressures
equal to or more than 0.5 psig.

The water heater must not be piped with gas supply
pressures in excess of 0.5 psig. If overpressure has
occurred, such as through improper testing of the gas
lines or malfunction of the supply system, the gas valve
must be checked for safe operation.
When connections are made, check for gas leaks at all
joints. Apply some soapy water to all gas fittings. Soap
bubbles are a sign of a leak.

Danger: If you have a leak, shut off the
gas. Tighten appropriate fittings to stop
leak. Turn the gas on and check again
with a soapy solution. Never test for gas
leaks using a match or flame.

0 - 4,000 ft
(0 - 1,219 m)

4,000 ft - 8,000 ft
(1,219 m - 2,438 m)

Above 8,000 ft
(above 2,438 m)

Table 4

Burner output at altitudes greater than 4,000 ft (1,219
m) will be electronically reduced once the control board
has been properly adjusted.

no
modification

contact CEC for detailed

no modification

instructions

2.12 Measuring gas pressure

To measure and verify if adequate gas pressure is being
delivered to the water heater, first run a high hot water
flow rate and operate other gas equipment on the same

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17

Appliance details

2.13 Water connections

When facing the heater, the ¾” cold water inlet is on the
bottom right and the hot water outlet is on the bottom
left. Install the heater centrally in the building if possible
and make hot water piping runs as short as possible.

INLET FILTER
SCREEN

HOT

Fig. 24

B THE USE OF A UNION WHEN CONNECTING

BOTH WATER PIPES TO THE INLET AND
OUTLET CONNECTIONS IS RECOMMENDED,
THIS WILL FACILITATE ANY NECESSARY
SERVICING AND REQUIRED CLEANING OF
THE INLET WATER PARTICLE SCREEN.

Although water piping throughout the building may be
other than copper, we recommend that copper,
galvanized or suitably rated stainless steel flex line
piping be used for the water heater connections (follow
local codes if more stringent). Never sweat any rigid
piping directly to or beneath the water connections,
damage can occur to the internal water valve from
heating of the pipe. Plastics or other PEX type plumbing
line materials are not suitable for connecting directly to
the water heater. Keep water inlet and outlet pipes to no
less than ¾" (19.05mm) diameter to allow the full flow
capacity.
If the cold and hot connections to the heater are
reversed, the heater will not function. Be certain there
are no loose particles or dirt in the piping. Blow out or
flush the lines before connecting to the water heater.
Full port valves should be installed on both the cold
water supply and hot water outlet lines to facilitate
servicing the heater (see Fig. 25). For installation on a
private well system with the use of a pressure tank, the
lowest pressure range setting recommended is 30-50
psi (2.07 and 3.45bar).

COLD

Connecting the pressure relief valve (PRV)

A listed pressure relief valve supplied with the heater
must be installed at the time of installation. No valve is
to be placed between the PRV and the heater. No
reducing coupling or other restriction may be installed
in the discharge line. The discharge line must be a
minimum of 4” above a drain and installed such that it
allows complete drainage of both the PRV and the line.
The location of the PRV must be readily accessible for
servicing or replacement, and be mounted as close to
the water heater as possible. See Fig. 25. To install the
PRV, a suitable fitting connected to an extension on a
“T” fitting can be sweated to the hot water line.
Support all piping.

Fig. 25 Plumbing Connections and Pressure Relief

Valve

18

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Appliance details

2.14 Electrical connections

Warning: For safety reasons,

disconnect the power supply to the
heater before any service or testing is
performed.

Warning: This heater must be
electrically grounded in accordance
with the most recent edition of the
National Electrical Code. NFPA 70. In
Canada, all electrical wiring to the
heater should be in accordance with
local codes and the Canadian Electrical
Code, CSA C22.1 Part 1. Do not rely
on the gas or water piping to ground the
metal parts of the heater.

The 250 SX requires an electrical power supply from a
120VAC 60Hz circuit and must be properly grounded.
A means for switching off the 120VAC power supply
must be provided.
The heater is wired as shown in the wiring diagram
(chapter 6, Fig. 36).

2.15 Operating instructions

B Before proceeding with the operation of the heater

make sure that the system is filled with water.

B Turn off power supply to heater.
B Open the cold water inlet supply to the heater fully.
B Open a hot water faucet to permit the water to fill the

heater and the piping and to eliminate the air trapped
in the system.

B Close the hot water faucet after the water flows freely

and all the air has escaped from the system. Turn on
power supply to heater. The water heater is now
ready to operate.

NOTE: A default temperature setting of
122 F will appear on the display screen.

i

2.16 For your safety read before
operating your water heater

Warning: If you do not follow these

instructions exactly, a fire or explosion
may result causing property damage,
personal injury or loss of life.

A. This appliance is equipped with electronic ignition for
lighting the main burners. When turning the heater on,
follow these instructions exactly.
B. Before operating the unit, set the On/Off switch to
the On ( I ) position.

WHAT TO DO IF YOU SMELL GAS

B Do not try to light any appliance.
B Do not touch any electric switch; do not use any

phone in your building.

B Immediately call your gas supplier from a neighbors

phone. Follow the gas supplier’s instructions.

B If you cannot reach your gas supplier, call the fire

department.

C. Use only your hand to turn the on/off control switch.
Never use tools. Follow these instructions exactly. If
control switch is jammed, close the gas supply and call
a qualified service technician. Attempted forceful repair
may result in a fire or explosion.
D. Do not use this appliance if any part has been under
water. Immediately call a qualified service technician to
inspect the appliance and to replace any part of the
control system and any gas control which has been
under water.

2.17 Lighting and operating instructions

B 1. STOP! Read the previous safety information.
B 2. The gas valve must be shut off by putting the ON/

OFF switch to position (0). Wait five (5) minutes to
clear out any gas. If you smell gas, STOP! Follow “B”
in the safety information above. If you do not smell
gas, go to the next step.

B 3. This appliance is equipped with electronic ignition

for lighting the main burners. When turning the
heater on, follow these instructions exactly.

B 4. Set the ON/OFF switch to the (I) position. In this

position, the water heater is ready to use.

B 5. Open a hot water tap.
B 6. The burners will remain on until the hot water tap

is turned off.

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19

Appliance details

NOTE: on a first time initial instal­lation or after gas line work has

i

been done, existence of air in the
gas line will cause ignition delay
when the hot water is turned on.
This will result in an error (EA) on
the units display screen. This is
normal. When this occurs, leave
the hot water running and wait 3-5
seconds, then reset the unit (Fig.
26, pos. 2). Wait for (EA) to disap­pear. The heater will begin to at­tempt ignition again, if the (EA)
reappears then repeat this same
process until all air has been bled
from the gas line.

When the heater is in operation you will hear its power
vent fan and burner operating. Upon turning off the hot
water flow the power vent fan will continue to operate
for up to 60 seconds to exhaust all flue gases. The
power vents fan speed is variable depending on the rate
of hot water used and the burner output.

TO TURN OFF GAS TO APPLIANCE

B Turn off the manual gas shut off on the supply line to

the heater and set the ON/OFF switch to the OFF (0)
position. Note: a manual gas shut off valve is not
supplied with the heater.

20

6 720 607 057

3 Operation instructions

Fig. 26

1 On/Off switch
2 Reset button
3 Program Key
4 Increasing temperature selector
5 Decreasing temperature selector
6 LCD display

Operation instructions

B Press buttons and in order to reach

requested temperature.

3.1 Power

On

B To start the appliance switch the button to position

(I).
LCD display the default temperature - temperature
factory setting 122°F (50°C).

Fig. 27

Off

B To shut down the appliance switch the button to

position (0).

Fig. 28

If the outlet water temperature is set too high, the heater
can produce temperatures that are too hot. A
temperature balance shower valve can automatically
mix in cold water to reduce such hot water temperature.
In the event of any temperature instability with the use
of a temperature balance shower valve, refer to shower
valve manufacturer's instructions for internal adjustment
setting. Adjustments should be made to the hottest
setting in the shower valve. Additionally the temperature
control of the heater can be lowered to produce a more
comfortable hot water temperature.

3.2 Temperature selection

To select water temperature outlet:

6 720 607 057

21

Operation instructions

)

)

Setting the water temperature

The desired temperature of the hot water can be adjusted on the front control panel of the heater.
The 250 SX has an electronically controlled gas valve that modulates the burner input in response to both varying
hot water flow rates and/or changes in any incoming and outgoing water temperatures.

Hot Water Flow and Temperature with Various Inlet Temperature (gpm/Fahrenheit)

7.00

6.00

5.00

4.00

3.00

2.00

Hot Water Flow (GPM

1.00

0.00
90 100 110 120 130 140 150

Inlet (ºF) 40 Inlet (ºF) 50 Inlet (ºF) 60 Inlet (ºF) 70

Hot water temperature (ºF)

Hot Water Flow and Te mperature with Various Inlet Temperature (lpm/Celsius)

24.00

20.00

16.00

12.00

8.00

Hot Water Flow (l/min

4.00

0.00

35 40 45 50 55 60 65

Inlet (ºC) 4 Inlet (ºC) 10 Inlet (ºC) 16 Inlet (ºC) 21

Fig. 29 Flow/temperature charts

Hot water temperature (ºC)

22

6 720 607 057

3.3 Use of remote control accessory

Operation instructions

Fig. 33 Reset button

If the problem persists, contact your installer.

Fig. 30 Remote control

The wireless remote control accessory and the
temperature selector buttons on the front of the water
heater operate identically. Contact your distributor or
CEC to order if the remote control accessory is
preferred. Modification of the water heaters interior
control unit (Fig. 29, component 12) is required when
programming the remote control with this heater.

NOTE: up to 6 remote controls can be
programmed for one single water heater,

i

each with a range distance of 98 ft (30 m).

3.4 Operation

B When a hot water tap is opened, main burner ignites

and LCD displays indication .

Fig. 31

B LCD blinks until selected temperature is reached.

3.5 Reset button

If the LCD shows the error symbol .
See the error code on LCD and consult
“Troubleshooting” section.

3.6 Program button

Program button can be used/programmed in the
appliance and in the remote control.

Programming “Program” function

Programming actions are similar for both controls
(appliance control pad and wireless remote control).

Fig. 34 “Program” key

B Press buttons and to select temperature to

be memorized.

B Hold “Program” button for 3 seconds to save

temperature.

When LCD stops blinking. Temperature is saved on
“Program”.

Using “Program” function

In order to select memorized temperature
B Press “Program” key.

LCD shows pre-memorized temperature, which is now
the hot water selected temperature.

3.7 Locked condition

Fig. 32

After following instructions indicated in
“Troubleshooting” section

B press reset button in order to make the appliance

ready-to-work.

6 720 607 057

This condition is only valid for appliances with more
then 1 controller (appliances with remote control).

Fig. 35 Locked condition

Whenever LCD shows the temperature setting
cannot be adjusted because the appliance is in use by
a user which already selected a different temperature.
Appliance will be automatically unlocked after closing
hot water tap.

23

Maintenance and service

4 Maintenance and service

Warning: Always turn off the electrical

power supply, turn off the manual gas
valve and turn off the manual water
control valves whenever servicing.

The unit should be checked once a year by a gas
technician. If repairs are needed, the repairs should be
done by a gas technician

To remove front cover

B Remove plastic decals on front panel (Page 5, Fig.

4).

B Loosen the two Philips head screws located behind

decals.

B Lift front cover panel upward and remove.

Systems and parts that should be checked at
least once a year

Reference diagrams on pages 29 and 30.

• Venting system

• Burners -see page 29 for observation window

• Manual operation of the pressure relief valve to insure
correct operation

• Periodic cleaning of the water filter screen, see Fig.
24, chapter 2.13.

• Flushing the heat exchanger with a descaling
solution if mineral build up is evident. Scale build up
will shorten the life of the water heater, descale heat
exchanger thoroughly and repeat annually depending
on mineral content of ground water.

5 Troubleshooting

heater will communicate the source by these error
codes.

BURNERS DO NOT IGNITE WHEN HOT WATER IS
TURNED ON

• Cold incoming water connection made to

wrong side of heater

Make sure cold water inlet connection is plumbed to
the right side of heater when facing unit

• Water flow rate at hot water tap is too low
A minimum of 0.8 gallon/minute (3 l/m) is required to
activate the heater

• Cold water inlet filter screen is dirty
Remove water inlet filter screen and clean. The
screen is located at the inlet connection to the water
heater, disconnecting the main cold supply line at the
heater is required. Check and clean faucet aerator
screens too.

• Crossover in plumbing
The heater activates when there is sufficient water
flow through its water valve, a minimum of 0.8 gallon/
minute (3 l/m) is required. If there is a crossover in the
plumbing, the necessary hot water flow rate through
the unit may not be reached, even though the flow at
the hot water tap is sufficient. A plumbing crossover
can be caused by a failed washer at a single lever
faucet, incorrect plumbing or a faulty mixing valve in
the piping. The crossover will create a back pressure
on the water heater and prevent an adequate flow of
water through it. To confirm there is no crossover in
the plumbing, shut off the cold water supply feed to
the water heater. Individually open each of the hot
water taps. There should be no water flowing under
a constant pressure. If there is a constant flow of
water then the plumbing crossover must be
corrected before the heater can operate properly.

Introduction

The 250 SX burner is activated by a water flow valve.
Numerous water related problems can cause this water
valve to malfunction such as: Insufficient water flow
volume to activate the burners at its minimum flow
requirement; Dirt in the water flow valve causing it to
malfunction; Sediment build-up in faucet aerators, or
shower heads; Uneven pressures between cold and hot
(with single lever mix valves); and Plumbing crossovers.
These water flow related problems can cause the
heater to deliver less than its full output, or to fail to
ignite or to shut down completely.
Problems stated below in upper case and in bold face
should be investigated when there is a problem with the
performance of the water heater but there is NO error
code on the heater's LCD display or wireless remote
control.
Any failures that result in a displayed error code are
referenced on page 26. A Functional Scheme of the
250 SX is detailed on page28. If there is a problem
with the installation, venting or operation of the unit, the

24

WATER IS TOO HOT

• Temperature selection too high
Lower temperature adjustment on heater or wireless
remote control accessory, see chapter 3.2.

WATER IS NOT HOT ENOUGH

• Temperature selection too low
Increase temperature adjustment on heater or
wireless remote control accessory, see chapter 3.2

• Btu input is too low due to inadequate gas line

sizing

See specifications in chapter 2.10 - 2.12. The 250
SX requires adequate gas pressure to reach desired
temperatures, to compensate for inadequate gas
supply or lack of gas pressure the 250 SX will
effectively reach the selected output temperature by
reducing the hot water flow rate. Its motorized water
valve makes this adjustment

• Cold water is mixing with the hot water outlet

(crossover)

6 720 607 057

Troubleshooting

Test by following 4th bullet under BURNERS DO
NOT IGNITE WHEN HOT WATER IS TURNED ON.

LOW WATER FLOW/PRESSURE

• Too many hot water applications are being

used simultaneously or too much flow is being
demanded

The 250 SX will effectively support two 2.0-2.5 gpm
shower heads simultaneously or multiple sink
applications. Greater draws will result in increased
pressure drop and reduced flow at taps. See flow/
temperature chart on page 22.

• Btu input is too low due to inadequate gas line

sizing

See specifications in chapter 2.10 - 2.12. The 250
SX requires adequate gas pressure to reach
expected temperatures and flow rates, to
compensate for inadequate gas supply or lack of gas
pressure the 250 SX will effectively reach the
selected output temperature, but only by reducing
the hot water flow rate. Its motorized water valve
makes this adjustment. Proper gas pressure will
need to be delivered before the motorized water
valve will allow greater flow rates through it. Lowering
the set temperature will also allow increased water
flow rate through the motorized water valve. See
flow/temperature chart on page 22.

• Cold water inlet filter screen is dirty
Remove water inlet filter screen and clean. The
screen is located at the inlet connection to the water
heater, disconnecting the main cold supply line at the
heater is required. Check and clean faucet aerator
screens too.

control of the heater can be lowered to produce a
more comfortable hot water temperature.

• Inlet water pressure is erratic due to

fluctuating supply water pressure

For installation on a private well system with the use
of a pressure tank, the lowest pressure range setting
recommended is 30-50 psi (2.07-3.45 bar). The use
of a pressure reducing valve after the pressure tank
is also an effective way to maintain a constant water
pressure to the water heater. Watts brand 25AUB­¾” or N35B-¾” pressure relief valves or equivalent
are suggested.

NOISY BURNER / HEATER DURING OPERATION

•CO

range is out of adjustment. The cover must be

2

in place to confirm CO

readings. Operating with the

2

cover removed may cause a noisy or unstable burner.
See Chapter 9, CO

adjustments can only be done

2

by a certified gas technician with a calibrated CO
analyzer.

2

HOT WATER TEMPERATURE FLUCTUATES /
UNIT DEACTIVATED

• Unbalanced pressure in water lines
Any restriction caused by the water heater in the hot
water system can result in uneven pressures
between the cold and the hot. In such cases when
mixing cold water at the tap (manually or
automatically through a mix-type shower valve) the
lower hot water pressure may be overpowered by the
higher cold water pressure in the building and cause
the hot water flow rate to fall below the minimum rate
required. A pressure balance valve will help to
resolve this symptom.

• Temperature balance valves
If the outlet water temperature is set too high, the
heater can produce temperatures that are too hot. A
temperature balance shower valve can automatically
mix in cold water to reduce such hot water
temperature. In the event of any temperature
instability with the use of a temperature balance
shower valve, refer to shower valve manufacturer's
instructions for internal adjustment setting.
Adjustments should be made to the hottest setting in
the shower valve. Additionally the temperature

6 720 607 057

25

Troubleshooting

Display Cause Solution

E9 Temperature limiter opened circuit

(overheat). Trips at 220F (104C).

EA No ionization during safety time (safety time

out).

EC The ionization signal momentarily

disappeared more then 3 times in less then
30 seconds.

FA Leakage error (gas valves do not close gas

circuit).

F7 Ionization error (flame sensing at stand-by). Check control unit.*

E0 Internal software/hardware failure. Check control unit.*

A7 Hot water temperature sensor/receiver

defect (from control unit).

A9 Hot water temperature sensor/receiver mis-

assembled (from control unit).

Check connections.*
Check heat exchanger condition.*

Check gas pressure.*
Check that gas is not diluted with air, as a result
from recent gas pipeline rework.*.
Check if vent terminal is blocked (especially when
the appliance starts up for some seconds and then
looses ionization signal).*
Check ionization electrode.*
Check for a proper ground.*

Check gas valve and control unit.*

Check water temperature sensor/receiver and
connections.*
Check room area temperature where heater is
located, it must be above 36°F (2°C)

Check that the water temperature sensor/receiver is
properly assembled in the water pipe.*
Check if vent terminal is blocked or if vent terminal is
according with
In case of high altitude installation confirm that
necessary adjustment steps have been taken.*

chapter 2.9

.*

C1 FAN rotation too low at start-up (from

control unit).

C6 FAN rotation too low at operation (from

control unit).

C7 No rotational speed sensor signal from FAN Check fan and connections.*

CA Water flow signal over specified maximum

value

E2 Inlet temperature sensor fault Check water temperature sensor/receiver and

A2 Overheat protection fault Check connections to the overheat protection.*

Check supply voltage.*
Check fan and connections.*
Check control unit.*
Check if vent terminal is blocked or if vent terminal is
according with
Check CO

Check supply voltage.*
Check fan and connections.*
Check control unit.*
Check if vent terminal is according with

chapter 2.9

Check control unit.*
Check CO2 levels (see chapter9).*

Check water valve and flow sensor.*

connections.*
Check room area temperature where heater is
located, it must be above 36°F (2°C)

Check sensor continuity.*
Check heat exchanger sealings and walls.*

chapter 2.9

levels (see chapter9).*

2

.*

. *

Table 5

26

* By installer or service technician only.

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6 Electrical diagram

Electrical diagram

Fig. 36 Electrical scheme

1 Intlet water temperature sensor
2 Ionization sensor
3 Water flow sensor
4 Over heat protection
5 Temperature limiter
6 Gas valve
7 Fan
8 Water valve
9 AC Plug
10 Ignition electrode
11 Display PCB
12 ON/OFF switch
13 Fuse T 2,5A
14 Fuse T 3,15A
15 Terminal block
16 Ground post
17 Outlet water temperature sensor

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27

250 SX Functional scheme

7 250 SX Functional scheme

Fig. 37 Functional scheme

28

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Interior components diagram and parts list

8 Interior components diagram and parts list

8.1 Interior components

Fig. 38 Components

1 Cover
2 On/Off switch
3 Reset button
4 LCD display
5 Program button
6 Temperature switches
7 Flue gas collector
8 Mixer
9 Heat exchanger
10 Observation window
11 Inlet air duct
12 Control unit
13 Exhaust fan
14 Water valve
15 Gas valve

6 720 607 057

Fig. 39 Appliance overview

29

Interior components diagram and parts list

8.2 Components diagram

Fig. 40 Components Diagram

30

6 720 607 057

Interior components diagram and parts list

8.3 Parts list

Item Description Reference

1 Front cover 8 705 421 837
2 Shield 8 705 506 661
3 Heat exchanger 8 705 406 285
4 Heat exchanger top gasket 8 704 701 052
5 Clip 8 716 102 607
6 Heat exchanger bottom gasket 8 704 701 054
7 O-ring 8 700 205 147
8 Temperature sensor 8 700 400 015
9 Washer 1/2" 8 710 103 045
10 Wireform spring 8 714 606 002
11 Air inlet duct 8 705 700 097
12 Water filter 8 700 507 001
13 O-ring 8 700 205 134
14 Water valve with engine 8 708 505 016
15 Main burner 8 708 120 515
16 Fan / Burner gasket 8 704 701 050
17 Set of electrodes 8 708 107 020
18 Exhaust Fan 8 707 204 039
19 Gas / Air Mixer 8 705 700 115
20 Mixer / Fan gasket 8 704 701 059
21 Gas valve washer 8 704 701 062
22 Gas valve 8 707 021 019
23 Gas valve washer 8 700 103 014
24 Remote control 8 707 207 153
25 Control unit 8 707 207 133
26 Ignition cable 8 704 401 220
27 Cables / 24V 8 704 401 214
28 Cables 8 704 401 239
29 Power supply cord 8 704 401 221
30 Overheat cutoff fuse 8 700 400 019
31 Flue gas exhaust accessory 8 705 504 114
32 Combustion air inlet accessory 8 705 504 115
33 Flue gas collector 8 705 700 100
34 Flue gas collector collar 8 705 700 114
35 Cold water pipe 8 700 715 156
36 Hot water pipe 8 700 715 155
37 Air inlet screen 8 700 507 069
38 Crossover tube 8 700 715 247
39 Overheat sensor (ECO) 8 707 206 204

Table 6

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31

Special adjustment for measuring and adjusting CO2 levels

9 Special adjustment for measuring and adjusting CO2 levels

The CO2 can only be adjusted by a certified gas
technician with a calibrated CO

analyzer.

2

Caution: Converting the gas type can

only be done by a certified gas
technician with a calibrated CO

2

analyzer. Call CEC for conversion
instructions.

Caution: Adjustments must only be
carried out by authorized service
personnel only.

Caution: The appliance should always
be disconnected from the power supply
before any maintenance is carried out.

9.1 Adjusting the unit

Factory settings of this appliance are listed in table 7.
Further adjustment is only needed if optimal CO
is required in order to assure the minimum possible
CO

emissions. In this case a CO2 analyzer is required.

2

level

2

CO

adjustment at minimum gas flow (P2) - See

2

table 7.

Factory
setting

Nat. Gas Nat. Gas

max. input P1 9.50 % 8.00 % to 10.00 %

min. input P2 9.50 % 8.00 % to 10.00 %

LP Gas LP Gas

max. input P1 10.50 % 10.00 % to 11.00 %

min. input P2 10.50 % 10.00 % to 11.00 %

* Final reading must be confirmed with the front cover
on, CO

levels increase when the cover is installed.

2

Field settings
acceptable range

Table 7

B Press “Program” key and turn ON/OFF switch to

position ON.

9.1.1 CO2 measuring

B Loosen screw 1 (Fig. 41).
B Insert CO

analyzer into measuring port (Fig. 41,

2

pos. 1).

Fig. 41

1 Measuring point

9.1.2 Selecting adjustment mode

B ON/OFF switch in position OFF (0).

Fig. 42

LCD shows “P2” and the appliance is ready to be
adjusted.

B Open hot water tap.
The appliance will run constantly at minimum power

output and minimum water flow. This program step can
also be used to measure minimum output and minimum
water flow.

B Turn the screw in order to regulate the air-gas mixture

inside the ventilator until the CO

level required is

2

reached (Fig. 43, pos. 3).

CO

adjustment at maximum gas flow (P1) - See

2

table 7.

B Press , until “P1” appears.

B Open hot water tap.

The appliance will run constantly at maximum power
output and maximum water flow. This program step can
also be used to measure maximum output and maximum
water flow.

B Turn the screw in order to regulate the air-gas mixture

inside the ventilator until the CO

level required is

2

reached (Fig. 43, pos. 3).

32

6 720 607 057

NOTE: turning screw clockwise
decreases CO

i

counterclockwise increases it.

Caution: Faulty ignition or noisy
operation may occur if CO
adjusted outside the indicated range.

level, turning

2

levels are

2

Special adjustment for measuring and adjusting CO2 levels

Fig. 43 Adjusting

Leave “Program” mode

B Turn ON/OFF switch in position OFF and then ON

again.

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33

Protecting the environment

10 Protecting the environment

Packing

The packing box may be fully recycled as confirmed by
the recycling symbol .

Components

Many parts in the heater can be fully recycled in the end
of the product life. Contact your city authorities for
information about the disposal of recyclable products.

Saving water resources:

B Make sure you close all the taps after any use. Avoid

leaving the taps dripping. Repair any leaking tap.

B Whenever possible use taps with built-in water flow

limiters. They will give you the same comfort level
while saving water.

B Define the temperature you want, in the appliance or

with the remote control. This way you have the
precise water flow needed (mixing cold water to
regulate temperature will increase the water flow with
consequent waste of water).

For increased safety shut off the appliance from
the main water supply if your are staying away
from home for a considerable time.
At below freezing temperatures, disconnect the
plumbing connections to the heater and allow
the heater to drain.
To prevent any freeze damage, introduce short
bursts of compressed air (20-40 psi) through
these connections to remove the residual water
in the horizontal pipes and water valve.

34

6 720 607 057

11 Twelve Year Limited Warranty

Twelve Year Limited Warranty

General

Aquastar water heaters are warranted by the
Manufacturer (BOSCH) through Controlled Energy
Corp. Controlled Energy Corp. (CEC) will furnish a
replacement heat exchanger and will furnish a
replacement of any other part which fails in normal use
and service within the applicable periods specified
below, in accordance with the terms of this warranty.
The CEC replacement will be warranted for the
unexpired portion of the original warranty. This warranty
will be valid only for water heaters in possession of the
original purchaser as recorded on the warranty card.

The Heat Exchanger

If the heat exchanger fails within twelve (12) years after
the original installation and operation, CEC will furnish
a replacement heat exchanger. However, if the water
heater is installed in other than a single family dwelling,
this heat exchanger warranty is limited to two (2) years
from date of original installation and operation.

Exceptions

This warranty will not apply:

• 1. to defects or malfunctions resulting from failure to
properly install, operate or maintain the unit in
accordance with the printed instructions provided;

• 2. to damage or abuse, accident, neglect or freezing
and other acts of nature;

• 3. to damage resulting from operation with either the
flame sensor rod or overheat sensor removed;

• 4. to failure of the heat exchanger resulting from the
operation of the water heater in a corrosive
atmosphere or at water temperatures exceeding the
maximum rating, or if the water heater is not supplied
with potable water;

• 5. to defects or damage cause by any attachment
or modification, including any energy-saving device.

All Other Parts

If any other part fails within two (2) years after original
installation and operation, CEC will furnish a
replacement part free of charge.

Shipping costs

In addition to supplying the replacement part(s), CEC
will provide ground service delivery for these parts.
Expedited or upgraded shipping will be charged to the
customer.

Service Labor Costs

This warranty does not cover any labor costs
associated with service, removal or re-installation of
part(s). All such costs must be borne by the Purchaser.
Additionally, this warranty does not cover any labor
costs associated with service, removal or re-installation
of the original water heater or a replaced water heater.

NOTE: the water heater must be free of
damaging scale deposits and not subject

i

to gas pressures greater than those
shown on the rating plate, which must not
be altered, defaced or removed.

How to Make a Claim

Any claim for warranty parts should be made to your
local dealer, distributor or to CEC. If CEC, please
contact the Technical Support Department:

Controlled Energy Corp.
340 Mad River Park
Waitsfield, VT 05673
Phone: [phone]
www.controlledenergy.com/tech

In most cases, the dealer or distributor will be able to
promptly honor your claim and subsequently notify
CEC. However, all replacements are made subject to
validation by CEC of in-warranty coverage. The
damaged or defective item must be made available in
exchange for the replacement.

Miscellaneous

No one is authorized to make any other warranties on
behalf of CEC. It is expressly understood that the
replacement warranty of CEC shall be in lieu of any and
all other warranties, express or implied, including
warranties of merchantability or fitness for a particular
use or purpose, and further that CEC shall not be liable
for any loss or damage directly or indirectly arising from
the use of the hot water heater, or for any consequential
damages arising from such use (including damages
from water leakage). CEC’s sole liability with respect to
any defect shall be for the replacement of the defective
part(s). Some states do not allow such limitations and
exclusions, so the above may not apply to you.
This warranty gives specific legal rights. You may also
have other rights which vary from state to state.

6 720 607 057

35

Replacement Parts available from North American Distributor

CONTROLLED ENERGY CORP.

340 Mad River Park

Waitsfield, Vermont 05673

Phone [phone]

Fax [phone]

VULCANO Termodomésticos S.A.

Estrada de Cacia

3801 - 856 Aveiro - PORTUGAL

www.controlledenergy.com/tech

[e-mail]

Recycled paper © 2004 Controlled Energy Corporation,

Waitsfield, VT all rights reserved